The present invention relates to image forming and image transfer apparatus especially for use in electrostatic imaging using an intermediate transfer blanket and to toner materials especially useful for electrostatic imaging using an intermediate transfer member.
The use of an intermediate transfer member in electrostatic imaging is well known. Generally, toner materials for use with such blankets are similar to those used for direct transfer from a photoreceptor to a final substrate, such as paper.
Various types of intermediate transfer members are known and are described, for example in U.S. Pat. Nos. 3,862,848, 4,684,238, 4,690,539, 4,531,825, 4,984,025, 5,047,808, 5,089,856, 5,335,054, U.S. patent applications Ser. No. 08/116,198, METHOD AND APPARATUS FOR IMAGING USING AN INTERMEDIATE TRANSFER MEMBER, filed Sep. 3, 1993 now U.S. Pat. No. 5,636,349 U.S. Ser. No. 07/400,717; METHOD AND APPARATUS FOR IMAGING USING AN INTERMEDIATE TRANSFER MEMBER, filed Aug. 30, 1989 now U.S. Pat. No. 5,555,185 U.S. Ser. No. 08/115,803; LIQUID DEVELOPER IMAGING SYSTEM HAVING A HEATED INTERMEDIATE TRANSFER MEMBER, filed Sep. 3, 1993 now U.S. Pat. No. 5,572,274 Ser. No. 07/351,546 COLOR IMAGING SYSTEM, filed May 15, 1989 now U.S. Pat. No. 5,559,376 and U.S. patent application Ser. No. 08/321,538 filed Oct. 11, 1994 titled IMAGING APPARATUS AND INTERMEDIATE-TRANSFER MEMBER THEREFOR to David EDAN et al., now abandoned, the specifications of all of which are incorporated herein by reference.
Removable intermediate transfer blankets for attachment to a drum for use in electrostatic images are described in a number of the above referenced patents and applications.
It has been found that the lifetime of such blankets appears to be limited at least in part by loss of surface properties of the blanket. In particular, such blankets are generally coated with a release layer, preferably a silicone release material. It appears that the release properties of the release material deteriorates with use.
In U.S. Pat. No. 5,192,638, the specification of which is incorporated herein in its entirety, Landa et al introduced a new liquid toner comprising a carrier liquid such as a light mineral oil and pigmented toner particles having, fibrous extensions. The mineral oils described in the above referenced patent were ISOPAR L and M (TM) type saturated hydrocarbon liquids having a high Kauri-Butanol number and a high resistivity. Many other mineral oils such as MARCOL 82 or other carrier liquids for liquid toner as are known in the art, are also suitable for the toner type of U.S. Pat. No. 5,192,638, depending on the overall characteristics specified for the toner. MARCOL 82 has a very low volatility and images produced from toners that use MARCOL 82 generally have poor abrasion resistance.
A characteristic of these toners is that they solvate the carrier liquid at elevated temperatures but are substantially insoluble in the carrier liquid at room temperature. Other patents and publications that describe preferred embodiments of this toner type and additives useful in the toner are U.S. Pat. Nos. 5,300,390; 5,286,593; 5,208,130; 5,266,435; 5,264,313; and 5,225,306 and in PCT publications WO 94/02887 the disclosures of which are incorporated herein by reference.
The present invention seeks to provide, in one aspect thereof, improved image transfer apparatus using an intermediate transfer member and a liquid toner and having an improved longevity of the intermediate transfer member.
The present invention further seeks to provide, in a second aspect thereof, an improved liquid toner that, when used with an intermediate transfer member results in an improvement in the life of the intermediate transfer member over what it would have been with prior art toners.
The present invention further seeks to provide, in a third aspect thereof, liquid toner components for use in the liquid toner of the invention.
There is thus provided in accordance with a preferred embodiment of the invention, imaging apparatus comprising:
an imaging surface having a liquid toner image formed thereon, said image comprising toner particles and carrier liquid, wherein the carrier liquid comprises as a major component, a liquid, preferably a liquid hydrocarbon, that evaporates relatively quickly at room temperature, and as a minor component, a liquid, preferably a liquid hydrocarbon, that evaporates relatively slowly at room temperature; and
an intermediate transfer member having a release outer layer that receives the toner image from the imaging surface and from which it is subsequently transferred.
There is further provided in accordance with a preferred embodiment of the invention, an imaging apparatus comprising:
an imaging surface having a liquid toner image formed thereon, said image comprising fibrous toner particles and carrier liquid, said fibrous toner particles comprising a polymer portion and pigment dispersed in said polymer portion, said polymer portion comprising a surface of said fibrous toner particles and being insoluble in said carrier liquid at temperatures below 40xc2x0 C. so that the polymer portion will not dissolve or solvate in storage, and solvatable by said carrier liquid only at temperatures above 50xc2x0 C., and said carrier liquid comprising, as a major component, first liquid hydrocarbon having a first rate of evaporation, and, as a minor component, second liquid hydrocarbon having a second rate of evaporation which, at room temperature, is at least an order of magnitude less than the first rate of evaporation; and
an intermediate transfer member having a release outer layer that is capable of receiving toner images from the imaging surface and subsequently transferring the images to a further surface.
Preferably, the release outer layer solvates the carrier liquid and is swelled by it.
There is further provided in accordance with a preferred embodiment of the invention a liquid developer comprising:
toner particles; and
carrier liquid, wherein the carrier liquid comprises as a major component, a liquid, preferably a liquid hydrocarbon, that evaporates relatively quickly at room temperature, and as a minor component, a liquid, preferably a liquid hydrocarbon, that evaporates very slowly at room temperature.
There is further provided in accordance with a preferred embodiment of the invention, a liquid toner comprising:
fibrous toner particles and carrier liquid;
said carrier liquid comprising, as a major component, first liquid hydrocarbon having a first rate of evaporation, and, as a minor component, second liquid hydrocarbon having a second rate of evaporation which, at room temperature, is at least an order of magnitude less than the first rate of evaporation; and
said fibrous toner particles comprising a polymer portion and pigment dispersed in said polymer portion, said polymer portion comprising a surface of said fibrous toner particles and being insoluble in said carrier liquid at temperatures below 40xc2x0 C. so that the polymer portion will not dissolve or solvate in storage, and solvatable by said carrier liquid only at temperatures above 50xc2x0 C.
Preferably, said minor component comprises between 0.2 and 2% and wherein said major component comprises between 98% and 99.7% of the total amount of said carrier liquid.
Preferably, the major component evaporates at least about an order of magnitude more quickly than the minor component.
Preferably, the major component has a vapor pressure at 100xc2x0 F. of greater than 0.05 psia when measured according to ASTM standard D 2879.
There is further provided, in accordance with a preferred embodiment of the invention, a mixture of liquid hydrocarbons substantially comprising between 0.5 and 4% of a substantially non-conducting liquid, preferably, a liquid hydrocarbon, that evaporates very slowly at room temperature and between 96% and 99.5% of a substantially non-conducting liquid, preferably a liquid hydrocarbon, that evaporates at least an order of magnitude more quickly.
Preferably, the mixture further comprises a charge director for liquid toner particles.
In a preferred embodiment of the invention, the carrier liquids are hydrocarbons wherein the hydrocarbon that evaporates relatively quickly has a vapor pressure at 100xc2x0 F. of greater than 0.05 psia when measured according to ASTM standard D 2879 and a 95% evaporation time at room temperature of less than 10 hours, preferably, less than 6 hours and the liquid hydrocarbon that evaporates relatively slowly has an evaporation time at least about an order of magnitude greater than 10 hours. Alternatively, other carrier liquids suitable for use in liquid toners such as fluorocarbons, silicones, etc., may be used in the practice of the broadest aspects of the invention.
In a preferred embodiment of the invention the release coating absorbs the carrier liquid and is swelled by it.